HomeMy WebLinkAboutWPO200400091 Calculations 2005-06-13 1 ,
EROSION AND SEDIMENT CONTROL NARRATIVE
FOR
JEFFERSON QUARRY BUILDING
May 24th 2005
LOCATION:
Tax Map 60 Parcel 48A
Jack Jouett District, Albemarle County, Virginia
6sC.PC
� m ae OWNER:
Reviewed and Approved by the George Barlow
Community Development Department Charlottesville. VA
Date: 13Ju 0E1 Tool'
File#: '• - .._
i cw. —311111§'
Signature DEVELOPER:
Turner Enterprises
P.O. Box 5347
Charlottesville, VA 22903
Attn: David Turner
PREPARED BY:
Rivanna Engineering & Surveying, Inc.
P. O. Box 154
Palmyra, VA 22963
(804) 589-8395
F: (804) 589-6327
RESI@CSTONE.NETLi
_
JUN 10 2005
A. MINIMUM STANDARDS (MS):
All applicable Virginia Erosion and Sediment Control Regulations and Minimum Standards
shall be adhered to during all phases of construction. These include, but are not limited to
the following:
1. STABLIZATION OF DENUDED AREAS:
Permanent or temporary soil stabilization shall be applied to bare areas within seven days
after final grade is reached on any portion of the site. Temporary soil stabilization shall be
applied within seven days to denuded areas that may not be at final grade, but will remain
dormant or undisturbed for longer than 30 days. Permanent stabilization shall be applied
at areas that are to be left dormant for more than 1 year.
2. STABILIZATION OF SOIL STOCKPILES:
During construction of the project, soil stockpiles shall be stabilized or protected with
sediment trapping measures. The applicant is responsible for temporary protection and
permanent stabilization of all soil stockpiles on site as well as soil intentionally transported
from the project site.
3. PERMANENT VEGETATIVE COVER
A permanent vegetative cover shall be established on denuded areas not otherwise
permanently stabilized. Permanent vegetation shall not be considered established until a
ground cover is achieve that, in the opinion of the county Inspector, is uniform and mature
enough to survive to inhibit erosion.
4. TIMING & STABILIZATION OF SILT TRAPPING MEASURES:
Sediment basins and traps, perimeter dikes, sediment barriers and other measures
intended to trap sediment shall be constructed as a first step in any land disturbing activity
and shall be made functional before upslope land disturbance takes place.
5. STABILIZATION OF EARTHEN STRUCTURES:
Stabilization measures shall be applied to earthen structures such as dams, dikes and
diversions immediately after installation.
6. SEDIMENT TRAPS AND BASINS:
A sediment basin shall control surface runoff from disturbed areas that is comprised of
flow from drainage areas greater than or equal to three acres. The sediment basin shall
be designed and constructed to accommodate the anticipated sediment loading for the
land disturbing activity. The outfall device or system device shall take into account the
total drainage area flowing through the disturbed area to be served by the basin.
7. CUT AND FILL SLOPES:
Cut and fill slopes shall be designed and constructed in a manner that will minimize
erosion. Slopes that are found to be eroding excessively within one year of permanent
stabilization shall be provided with additional slope stabilizing measures until the problem
is corrected.
8. CONCENTRATED RUN-OFF DOWN CUT OR FILL SLOPES:
Concentrated runoff shall not flow down cut or fill slopes unless contained within an
adequate temporary or permanent channel, flume, or slope drain structure.
1
9. WATER SEEPS FROM A SLOPE FACE:
Whenever water seeps from a slope face, adequate drainage or other protection shall be
provided.
10. STORM SEWER INLET PROTECTION:
All storm sewer inlets that are made operable during construction shall be protected so
that sediment-laden water cannot enter the conveyance system without first being filtered
or otherwise treated to remove sediment.
11. STABILIZATION OF OUTLETS:
Before newly constructed stormwater conveyance channels are made operational,
adequate outlet protection and any required temporary or permanent channel lining shall
be installed in both the conveyance channel and receiving channel.
12. WORK IN LIVE WATERCOURSES:
When work in a live watercourse is performed, precautions shall be taken to minimize
encroachment, control sediment transport and stabilize the work area to the greatest
extent possible during construction. Nonerodible material shall be used for the
construction of causeways and cofferdams. Earthen fill may be used for these structures if
armored by nonerodible cover materials.
13. CROSSING A LIVE WATERCOURSE:
When a live watercourse must be crossed by construction vehicles more than twice in any
six month period, a temporary stream crossing constructed of nonerodible materials shall
be provided.
14. APPLICABLE REGULATIONS:
All applicable federal, state and local regulations pertaining to working in or crossing live
watercourses shall be met.
15. STABILIZATION OF BED AND BANKS
The bed and banks of a watercourse shall be stabilized immediately after work in the
watercourse is completed.
16. UNDERGROUND UTILITIES:
Underground utilities shall be installed in accordance with the following standards in
addition to other criteria:
a. No more than 500 linear feet of trench may be opened at one time.
b. Excavated material shall be placed on the uphill side of trenches
c. Effluent for dewatering operations shall be filtered or passed through approved
sediment trapping device, or both, and discharged in a manner that does not adversely
affect flowing streams or offsite property.
d. Material used for backfilling trenches shall be properly compacted in order to minimize
erosion and promote stabilization.
e. Restabilization shall be accomplished in accordance with these regulations.
f. Applicable safety regulations shall be complied with.
2
17. CONSTRUCTION ACCESS ROUTES:
Where construction vehicle access routes intersect paved public roads, provisions shall
be made to minimize the transport of sediment by vehicular tracking onto paved surfaces.
Where sediment is transported on to a public road surface, the road shall be cleaned
thoroughly at the end of each day. Sediment shall be removed by shoveling or sweeping
and transported to a sediment control disposal area. Street washing shall be allowed only
after sediment is removed in this manner. This provision shall apply to individual lots as
well as to larger land disturbing activities.
18. TEMPORARY E&S CONTROL MEASURE REMOVAL:
All temporary erosion and sediment control measures shall be removed within 30 days
after final site stabilization or after temporary measures are no longer needed, unless
otherwise authorized by the local program authority. Trapped sediment and the disturbed
soil areas resulting from the disposition of temporary measures shall be permanently
stabilized to prevent further erosion and sediment.
19. ADEQUACY OF RECEIVING CHANNELS:
Properties and waterways downstream from the development site shall be protected from
sediment deposition, erosion and damage, due to increases in volume, velocity and peak
flow rates of stormwater runoff for the stated frequency storm of 24-hour duration.
B1. PROJECT DESCRIPTION:
The purpose of this project is to construct a 3-story office building and associated parking.
The total area to be disturbed by this project will be 2.2 acres.
B2. EXISTING SITE CONDITIONS:
The site is densely wooded with an existing stormwater management facility in the
southeast corner that services the adjacent parcel. This facility will be renovated as part
of this project.
B3. ADJACENT AREAS:
The site is bounded by on the North by Route 601, on the East by an office building, on
the South by a railroad, and on the West by a vacant parcel.
B4. SOIL DESCRIPTIONS:
According to the Albemarle County Soils Survey conducted by the United States
Department of Agriculture Soil Conservation Service, the primary soil types that may be
disturbed during this scope of work have been identified as the following:
1. Udorthents, loamy (88) — Permability is slow, the hazard of erosion moderate.
B5. CRITICAL AREAS:
There are no critical areas associated with this portion of the project.
3
B6. EROSION AND SEDIMENT CONTROL MEASURES:
Unless otherwise indicated, all erosion and sediment control practices will be constructed
and maintained according to the minimum standards and specifications as set forth in the
Virginia Erosion and Sediment Control Handbook, latest edition. The minimum standards
of the Virginia Erosion and Sediment Control Regulations shall be adhered to unless
otherwise waived or approved by variance.
TEMPORARY CONSTRUCTION ENTRANCE (CE) -3.02
An asphalt pad shall be constructed at the entrance of the project site to provide a means
of removing sediment from the tires of construction vehicles leaving the work site. The
Contractor shall remove any mud from the existing road surface by means of sweeping
and shoveling, in the event the stone pad is not adequate in sediment removal.
STORM DRAIN INLET PROTECTION (IP) -3.07
A sediment filter or an excavated impounding area around a storm drain drop inlet or curb
inlet used to prevent sediment from entering storm drainage systems prior to permanent
stabilization of the disturbed area. Location and details of inlet protection are shown on
the plans.
TEMPORARY DIVERSION DIKE (DD) -3.09
A temporary diversion dike will be installed before site grading begins, for the purposes of
diverting storm and sediment-laden runoff to the appropriate outlet or trapping facility.
Location and details are shown on the plans.
TEMPORARY SEDIMENT BASIN (SB) -3.13
A temporary sediment basin will be installed before site grading begins, for the purpose of
detaining sediment-laden runoff from disturbed areas. The total disturbed area draining to
the site is - 2.0 Acres, which requires 134 cu yd. of wet volume. Inlcuding offsite
(unidisturbed) areas the total drainage area is 7.15 Acres and would require 480 cu yd of
storage. Since the majority of the contributing drainage area is offsite, the basin has been
designed with a wet storage volume of 290 cu yd, more than twice the minumum required
for the disturbed area and approximately 60% of the required volume for a totally
disturbed site. Location and details of the sediment traps are shown on the plans.
DUST CONTROL (DC) -3.39
A variety of methods are available to prevent surface and air movement of dust from
exposed soil surfaces and reduce the presence of airborne substances which may
present health hazards, traffic safety problems or harm animal or plant life.
B7. PERMANENT AND TEMPORARY STABILIZATION:
SURFACE ROUGHENING -3.29
Disturbed areas to be seeded and mulched shall be left in a roughened condition to help
decrease runoff velocities and aid in the establishment of vegetation.
TOPSOILING-3.30
Topsoil may be stripped from the area to be graded and stockpiles for later use. All
stockpiles which will be left dormant for more than 30 days shall be temporarily seeded. A
topsoil stockpile may be selected onsite by the developer and shall be temporarily
protected with surrounding silt fencing.
4
TEMPORARY SEEDING —3.31
Temporary soil stabilization shall be applied within 7 days to denuded areas that may not
be at final grade, but will remain dormant (undisturbed) for longer than 30 days and less
than 1 year. This includes, but is not limited to areas such as soil stockpiles. Seeded
areas shall be limed when necessary at a rate of 2 tons per acre, and fertilized at a rate of
450 lbs. per acre of 10-20-20 (10 lbs. per 1,000 square feet) or equivalent. A Temporary
Seeding Schedule is attached for proper seed selection.
PERMANENT SEEDING—3.32
A perennial vegetative covering shall be established on disturbed areas within 7 days of
being brought to final grade on areas not otherwise protected. Selection of the seed
mixture shall depend on the time of year it is to be applied according to the Permanent
Seed Schedule as shown on the drawing. Seeded areas shall be limed when necessary
at a rate of 2 tons per acres, and fertilized at a rate of 1,000 lbs. per acre of 10-20-10 (10
lbs. per 1,000 square feet) or equivalent.
MULCHING—3.35
All seeded areas shall be mulched with straw immediately following seeding operations.
Straw mulch shall be applied at a rate of two tons per acre.
SOIL STABILIZATION BLANKETS AND MATTING —3.36
Soil stabilization matting shall be applied in the conveyance areas of the designed
diversions to help reduce velocities and aid in the establishment of vegetation. A detail
showing the proper materials and installation is shown on the plan.
B8. SOIL STOCKPILES AND BORROW AREAS
Debris such as tree's and stumps shall be mulched onsite, or removed from the site and
disposed of in accordance with local regulations. No offsite soil borrow areas or stockpiles
are expected.
B9. STORM WATER MANAGEMENT:
The temporary sediment basin shall be converted to a permanent Stormwater
management facility upon site stabilization.
5
B10. MAINTENANCE SCHEDULE:
A program of maintenance for the erosion and sediment controls specified in this narrative
and shown on the plans are recommended as follows:
1. The Site Superintendent or his representative shall make a visual inspection of all
erosion and sediment controls on a daily basis until the site is stabilized and especially
after a heavy rainfall to assure that all controls are in place and that none have been
damaged. Any damaged control shall be repaired prior to the end of each workday to
include re-seeding if necessary.
2. All silt trapping devices shall be cleaned out at 50 percent capacity and sediment shall
be disposed of by spreading on site or hauling away if not suitable for fill.
3. Gravel outlets shall be checked regularly for sediment buildup that may prevent
drainage. Controls shall be inspected and repaired after each rainfall and cleaned if
sediment has accumulated to half of the device's original height.
4. All earthen structures such as diversion dikes and berms shall be checked daily during
construction for breaching by equipment. Repairs shall be made immediately.
5. Silt fences shall be checked after each rainstorm to assure they have not fallen or
become clogged with silt. All repairs shall be made immediately.
6. All seeded areas shall be inspected regularly to see that good stand is maintained.
Areas will be re-fertilized and re-seeded as necessary.
7. After construction operations have ended and disturbed areas have been stabilized, all
berms and sediment-trapping devices may be removed After removal, the ground shall
be restored to its natural or proposed condition to include establishment of permanent
vegetation. Removal of any control is contingent upon approval of the County
Inspector.
6
RESERVOIR REPORT
Reservoir Number: 2
Name: Sediment Basin
[RATING CURVE LIMIT]
Minimum Elevation = 555.00 (ft)
Maximum Elevation = 564 .00 (ft)
Elevation Increment = 0.10 (ft)
[STAGE STORAGE INFORMATION]
Storage Method: User-Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative
Volume
(ft) (sq ft) (sq ft) (cu ft) (cu ft)
_
1 554.95 0.00 0.00 0.00 0.00
2 555.00 2464.00 1232.00 61.60 61.60
3 557.00 2901.00 2682.50 5365.00 5426.60
4 558.00 3483.00 3192.00 3192.00 8618.60
5 560.00 4727.00 4105.00 8210.00 16828.60
6 562.00 6271.00 5499.00 10998.00 27826. 60
7 564.00 8063.00 7167.00 14334.00 42160. 60
[DISCHARGE INFORMATION]
Structure Number: 1
Type: Trapezoidal Weir
Name: Spillway
Structure Number: 2
Type:
Name: Outlet - Sed Basin
7
[RESERVOIR STAGE STORAGE/DISCHARGE]
Elevation Stage Area Storage Discharge
(ft) (ft) (sq ft) (cu ft) (cfs)
555.00 0.00 0.00 0.00 0.00
555. 10 0.10 2485.85 124.29 0.00
555.20 0.20 2507.70 373. 97 0.00
555.30 0.30 2529.55 625.83 0.00
555.40 0.40 2551.40 879.88 0.00
555.50 0.50 2573.25 1136.11 0.00
555.60 0.60 2595.10 1394.53 0.00
555.70 0.70 2616. 95 1655.13 0.00
555.80 0.80 2638.80 1917. 92 0.00
555.90 0. 90 2660. 65 2182.89 0.00
556.00 1.00 2682.50 2450.05 0.00
556.10 1.10 2704.35 2719.39 0.00
556.20 1.20 2726.20 2990. 92 0.00
556.30 1.30 2748.05 3264.63 0.00
556.40 1.40 2769.90 3540.53 0.00
556.50 1.50 2791.75 3818.61 0.00
556.60 1. 60 2813.60 4098.88 0.00
556.70 1.70 2835.45 4381.33 0.00
556.80 1.80 2857.30 4665.97 0.00
556.90 1. 90 2879.15 4952.79 0.00
557.00 2.00 2901.00 5241.80 0.00
557.10 2.10 2959.20 5534.81 0.00
557.20 2.20 3017.40 5833. 64 0.00
557.30 2.30 3075.60 6138.29 0.00
557.40 2.40 3133.80 6448.76 0.00
557.50 2.50 3192.00 6765.05 0.00
557.60 2.60 3250.20 7087.16 0.00
557.70 2.70 3308.40 7415.09 0.00
557.80 2.80 3366. 60 7748.84 0.00
557. 90 2.90 3424.80 8088.41 0.00
558.00 3.00 3483.00 8433.80 0.00
558.10 3.10 3545.20 8785.21 0.00
558.20 3.20 3607.40 9142.84 0.00
558.30 3.30 3669. 60 9506.69 0.00
558.40 3.40 3731.80 9876.76 0.00
558.50 3.50 3794 .00 10253.05 0.00
558.60 3.60 3856.20 10635.56 0.00
558.70 3.70 3918.40 11024.29 0.00
558.80 3.80 3980.60 11419.24 0.00
558. 90 3.90 4042.80 11820.41 0.00
559.00 4.00 4105.00 12227.80 0.00
559.10 4.10 4167.20 12641.41 0.00
559.20 4.20 4229.40 13061.24 0.00
559.30 4.30 4291.60 13487.29 0.00
559.40 4.40 4353.80 13919.56 0.00
559.50 4.50 4416.00 14358.05 0.00
559.60 4.60 4478.20 14802.76 0.00
559.70 4.70 4540.40 15253.69 0.00
559.80 4.80 4602.60 15710.84 0.00
559. 90 4.90 4664.80 16174.21 0.00
560.00 5.00 4727.00 16643.80 0.00
560.10 5.10 4804.20 17120.36 0.00
8
560.20 5.20 4881.40 17604.64 0.00
560.30 5.30 4958.60 18096.64 0.00
560.40 5.40 5035.80 18596.36 0.00
560.50 5.50 5113.00 19103.80 0.00
560. 60 5.60 5190.20 19618. 96 0.00
560.70 5.70 5267.40 20141.84 0.00
560.80 5.80 5344.60 20672.44 0.00
560. 90 5.90 5421.80 21210.76 0.00
561.00 6.00 5499.00 21756.80 0.00
561. 10 6.10 5576.20 22310.56 0.00
561.20 6.20 5653.40 22872.04 0.00
561.30 6.30 5730. 60 23441.24 0.00
561.40 6.40 5807.80 24018.16 0.00
561.50 6.50 5885.00 24602.80 0.00
561.60 6.60 5962.20 25195.16 0.00
(total 25 yr storm flow = 0.58 acre-ft or 25,264 cu. Ft)
561.70 6.70 6039.40 25795.24 0.00
561.80 6.80 6116.60 26403.04 0.00
561. 90 6.90 6193.80 27018.56 0.00
562.00 7.00 6271.00 27641.80 0.11
562.10 7.10 6360.60 28273.38 0.30
562.20 7.20 6450.20 28913. 92 0.55
562.30 7.30 6539.80 29563.42 0.84
562.40 7.40 6629.40 30221.88 1.18
562.50 7.50 6719.00 30889.30 1.55
562.60 7.60 6808.60 31565. 68 1. 95
562.70 7.70 6898.20 32251.02 2.38
562.80 7.80 6987.80 32945.32 2.84
562.90 7. 90 7077.40 33648.58 3.33
563.00 8.00 7167.00 34360.80 4.73
563.10 8.10 7256. 60 35081.98 7. 94
563.20 8.20 7346.20 35812.12 12.54
563.30 8.30 7435.80 36551.22 18.14
563.40 8.40 7525.40 37299.28 24.57
563.50 8.50 7615.00 38056.30 31.75
563.60 8.60 7704.60 38822.28 39.60
563.70 8.70 7794.20 39597.22 48.07
563.80 8.80 7883.80 40381.12 56.81
563. 90 8. 90 7973.40 41173. 98 65.12
564.00 9.00 8063.00 41975.80 71. 93
Maximum Storage = 41975.80 (cu ft)
Maximum Discharge = 71. 93 (cfs)
9
OUTLET STRUCTURE REPORT
Structure Number : 3
Type : Stand Pipe
Name : Outlet - Sed Basin
[RATING CURVE LIMIT]
Minimum Elevation = 557.00 (ft)
Maximum Elevation = 564.00 (ft)
Elevation Increment = 0.10 (ft)
[STAND PIPE INFORMATION]
[ORIFICE INFORMATION]
Diameter = 3.00 (ft)
Crest Length = 9.42 (ft)
Effective Crest Length = 8.42 (ft)
Orifice Coefficient = 0.60
Fractional Open Area = 0.90
[ORIFICE EQUATION]
Q = Co*A( (2gh) /k) ^0.5
[DEFINITIONS]
Co = Orifice Coefficient
A = Wetted Area, (sq ft)
[WEIR INFORMATION]
Crest Elevation = 562. 90 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
[WEIR EQUATION]
Q = Cw * L * H^exp
[DEFINITIONS]
Cw = Weir Coefficient
H = Headwater depth above inlet control section invert ft
L = Crest lenght ft
[OPTIONAL WEIR INFORMATION]
Structure Number : 1
Type : Rectangular Weir Suppressed
[WEIR INFORMATION]
Crest Length = 1.00 (ft)
Crest Elevation = 561.90 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
[RECTANGULAR SUPRESSED EQUATION]
Q = Cw * L * H^exp
10
[DEFINITIONS]
Cw = Weir Coefficient
H = Headwater depth above inlet control section invert
L = Crest lenght
[CULVERT INFORMATION]
Type : Circular Concrete - Square Edge with Headwall
[OUTLET STRUCTURE INFORMATION]
Diameter = 24 .00 (in)
Invert Elevation = 557.00 (ft)
Pipe Length = 30.00 (ft)
Slope = 0.02
Manning's n Value = 0.01
Orifice Coefficient = 0. 60
Tailwater Elevation = 556.40 (ft)
Number of Barrels = 1
[UNSUBMERGED EQUATION]
H/Diam = Hc/Diam+K* (Q/ (A*Diam^0.5) ) ^M-0.5*S
Coefficient K = 0.01
Coefficient M = 2.00
Q Maximum = 15.55
[SUBMERGED EQUATION]
H/Diam = c* (Q/ (A*Diam^0.5) ) ^2+Y-0.5*S
Coefficient c = 0.04
Coefficient Y = 0. 67
Q Minimum = 17.77
[DEFINITIONS]
H = Headwater depth above inlet control section invert, (ft)
Diam = Interior height of culvert barrel, (ft)
Hc = Specific head at critical depth (dc+Vc^2/2g) , (ft)
Q = Discharge, (cfs)
A = Full cross sectional area of culvert barrel, (sq ft)
S = Culvert barrel slope, (ft/ft)
11
[STAND PIPE STAGE VS. DISCHARGE]
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
(ft) (ft) (cfs) (cfs) (cfs) (cfs) (cfs)
557.00 0.00 0.00 0.00 0.00 0.00 0.00
557.10 0.10 0.00 0.00 0.00 0.07 0.00
557.20 0.20 0.00 0.00 0.00 0.23 0.00
557.30 0.30 0.00 0.00 0.00 0.49 0.00
557.40 0.40 0.00 0.00 0.00 0.82 0.00
557.50 0.50 0.00 0.00 0.00 1.25 0.00
557.60 0.60 0.00 0.00 0.00 1.73 0.00
557.70 0.70 0.00 0.00 0.00 2.29 0.00
557.80 0.80 0.00 0.00 0.00 2.92 0.00
557. 90 0.90 0.00 0.00 0.00 3.61 0.00
558.00 1.00 0.00 0.00 0.00 4.34 0.00
558.10 1.10 0.00 0.00 0.00 5.10 0.00
558.20 1.20 0.00 0.00 0.00 5. 92 0.00
558.30 1.30 0.00 0.00 0.00 6.74 0.00
558.40 1.40 0.00 0.00 0.00 7.59 0.00
558.50 1.50 0.00 0.00 0.00 8.47 0.00
558.60 1.60 0.00 0.00 0.00 9.35 0.00
558.70 1.70 0.00 0.00 0.00 10.24 0.00
558.80 1.80 0.00 0.00 0.00 11.12 0.00
558. 90 1.90 0.00 0.00 0.00 12.03 0.00
559.00 2.00 0.00 0.00 0.00 12. 91 0.00
559.10 2. 10 0.00 0.00 0.00 13.79 0.00
559.20 2.20 0.00 0.00 0.00 14.67 0.00
559.30 2.30 0.00 0.00 0.00 15.55 0.00
559.40 2.40 0.00 0.00 0.00 15.55 0.00
559.50 2.50 0.00 0.00 0.00 17.77 0.00
559. 60 2. 60 0.00 0.00 0.00 17.82 0.00
559.70 2.70 0.00 0.00 0.00 18.50 0.00
559.80 2.80 0.00 0.00 0.00 19.16 0.00
559. 90 2.90 0.00 0.00 0.00 19.79 0.00
560.00 3.00 0.00 0.00 0.00 20.41 0.00
560.10 3.10 0.00 0.00 0.00 21.01 0.00
560.20 3.20 0.00 0.00 0.00 21.59 0.00
560.30 3.30 0.00 0.00 0.00 22.16 0.00
560.40 3.40 0.00 0.00 0.00 22.71 0.00
560.50 3.50 0.00 0.00 0.00 23.25 0.00
560.60 3. 60 0.00 0.00 0.00 23.78 0.00
560.70 3.70 0.00 0.00 0.00 24.29 0.00
560.80 3.80 0.00 0.00 0.00 24.80 0.00
560.90 3. 90 0.00 0.00 0.00 25.29 0.00
561.00 4.00 0.00 0.00 0.00 25.78 0.00
561.10 4.10 0.00 0.00 0.00 26.26 0.00
561.20 4.20 0.00 0.00 0.00 26.72 0.00
561.30 4.30 0.00 0.00 0.00 27.18 0.00
561.40 4.40 0.00 0.00 0.00 27.64 0.00
561.50 4.50 0.00 0.00 0.00 28.08 0.00
561.60 4.60 0.00 0.00 0.00 28.52 0.00
561.70 4.70 0.00 0.00 0.00 28. 95 0.00
561.80 4.80 0.00 0.00 0.00 29.38 0.00
561. 90 4. 90 0.00 0.00 0.00 29.80 0.00
562.00 5.00 0.11 0.00 0.00 30.21 0.11
562.10 5. 10 0.30 0.00 0.00 30. 62 0.30
12
562.20 5.20 0.55 0.00 0.00 31.02 0.55
562.30 5.30 0.84 0.00 0.00 31.42 0.84
562.40 5.40 1.18 0.00 0.00 31.81 1.18
562.50 5.50 1.55 0.00 0.00 32.20 1.55
562. 60 5.60 1. 95 0.00 0.00 32.58 1.95
562.70 5.70 2.38 0.00 0.00 32.96 2.38
562.80 5.80 2.84 0.00 0.00 33.33 2.84
562. 90 5.90 3.33 0.00 0.00 33.70 3.33
563.00 6.00 3.84 0.00 0.89 34.07 4.73
563.10 6.10 4.38 0.00 2.51 34.43 6.89
563.20 6.20 4.94 0.00 4.61 34.79 9.55
563.30 6.30 5.52 0.00 7. 10 35.14 12.61
563.40 6.40 6.12 0.00 9.92 35.49 16.04
563.50 6.50 6.74 0.00 13.04 35.84 19.78
563.60 6.60 7.38 0.00 16.43 36.18 23.81
563.70 6.70 8.04 0.00 20.08 36.53 28.12
563.80 6.80 8.72 0.00 23. 63 36.86 32.36
563. 90 6.90 9.42 0.00 26.42 37.20 35.84
564.00 7.00 10.13 0.00 29.21 37.53 37.53
13
OUTLET STRUCTURE REPORT
Structure Number : 2
Type : Trapezoidal Weir
Name : Spillway
[RATING CURVE LIMIT]
Minimum Elevation = 557.00 (ft)
Maximum Elevation = 564.00 (ft)
Elevation Increment = 0.50 (ft)
[OUTLET STRUCTURE INFORMATION]
Crest Length = 10.00 (ft)
Angle of Walls = 45.0000
Crest Elevation = 563.00 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
[TRAPEZOIDAL EQUATION]
Q = Cw * ( L + 0.8H * tan ( ang/2.0 ) ) * H^exp
[DEFINITIONS]
Cw = Weir Coefficient
H = Headwater depth above inlet control section invert
L = Crest lenght
ang = Angle of the walls
[MAXIMUM DISCHARGE]
Q = 34.40 (cfs)
[WEIR STAGE VS. DISCHARGE]
Elevation (ft) Stage (ft) Discharge (cfs)
557.00 0.00 0.00
557.50 0.50 0.00
558.00 1.00 0.00
558.50 1.50 0.00
559.00 2.00 0.00
559.50 2.50 0.00
560.00 3.00 0.00
560.50 3.50 0.00
561.00 4.00 0.00
561.50 4.50 0.00
562.00 5.00 0.00
562.50 5.50 0.00
563.00 6.00 0.00
563.50 6.50 11. 97
564.00 7.00 34.40
14
FLOOD HYDROGRAPH REPORT
Hydrograph Number: 12
Name: Post Dev 25 Year
Type: Modified Rational
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 33.84 (cfs)
Time to Peak (Tp) = 10.00 (min)
Time of Base (Tb) = 25.00 (min)
Volume = 0.58 (ac-ft)
Time Step = 1.00 (min)
Flow Multiplier = 1.00
[RATIONAL HYDROGRAPH INFORMATION]
Flow Multiplier = 1.00
Receding Limb Factor = 1.50
[APPROXIMATE STORAGE]
Maximum Outflow = 0.00 (cfs)
Maximum Storage = 0.58 (cu ft)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN Runoff Coef
<None>
Overall Approximation 7.15 NA 0.72
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 10.00 (min)
[RAINFALL DESCRIPTION]
Distribution Type = Synthetic
Total Precipitation = 1.09 (in)
Return Period = 25 (yr)
Storm Duration = 0.17 (hr)
15
[Hydrograph Flow Values: Time vs. Flow]
[TIME CONCENTRATION - 10.00]
Time Time Incremental Cumulative Incremental Design
Interval Rainfall Rainfall Outflow Outflow
(min) (in) (in) (cfs) (cfs)
1 1.00 0.00 0.11 0.00 3.38
2 2.00 0.11 0.22 3.38 6.77
3 3.00 0.11 0.33 3.38 10.15
4 4.00 0.11 0.44 3.38 13.54
5 5.00 0.11 0.55 3.38 16.92
6 6.00 0.11 0. 66 3.38 20.30
7 7.00 0.11 0.76 3.38 23. 69
8 8.00 0.11 0.87 3.38 27.07
9 9.00 0.11 0. 98 3.38 30.46
10 10.00 0.11 1.09 3.38 33.84
11 11.00 0.00 1.09 -2.25 31.59
12 12.00 0.00 1.09 -2.26 29.33
13 13.00 0.00 1.09 -2.26 27.08
14 14.00 0.00 1.09 -2.26 24.82
15 15.00 0.00 1.09 -2.26 22.57
16 16.00 0.00 1.09 -2.26 20.31
17 17.00 0.00 1.09 -2.26 18.05
18 18.00 0.00 1.09 -2.26 15.80
19 19.00 0.00 1.09 -2.26 13.54
20 20.00 0.00 1.09 -2.26 11.28
21 21.00 0.00 1.09 -2.26 9.03
22 22.00 0.00 1.09 -2.26 6.77
23 23.00 0.00 1.09 -2.26 4.52
24 24.00 0.00 1.09 -2.26 2.26
25 25.00 0.00 1.09 -2.26 0.00
16